Posted
by
Soulskill
on Thursday March 10, 2011 @10:26AM
from the nobody-tell-the-tsa dept.

lukehopewell1 writes "It's official: using Wi-Fi on a plane can interfere with a pilot's navigational equipment, according to airline equipment manufacturers Honeywell Avionics and Boeing today. Boeing confirmed to ZDNet Australia that the issue does exist, but said it has not delivered any planes suffering the fault. 'Blanking of the Phase 3 Display Units has been reported during airline EMI (electromagnetic interference) certification testing of wireless broadband systems on various Next-Generation 737 aeroplanes,' Boeing said."

Go learn about RF. At the frequencies used by Wi-Fi a resonant antenna is only a few CMs long, ie about the length of common circuit traces on the PCB's. Even if you completely shield the control units RF can still leak inside through cabling. There is no magic way to design electronics that are RF immune*, it requires real world testing to discover such faults, as happened here.

The only way to make extremely RF tolerant electronics is to use analog vacuum tube based designs (the Russians continued using tube designs into the 90's).

It is pretty dubiously practical; but you can carry power over fiber(bright light on one end, photocell on the other). Both the max power per strand and the efficiency kind of suck; but that does allow you to(for low power systems about which you are rather paranoid) build a completely optocoupled device...

Rarely practical(and obviously wholly unhelpful for things like radar and radio communications gear, which explicitly rely on collecting RF); but the only thing stopping you is good sense...

You are entirely correct when you say that optically powered systems are unequal to the task of powering anything serious. We are talking under 2 watts/strand here. Nice if you want to put an electrically powered sensor right in the middle of 'if-it-sparks-here-everybody-will-die-horribly-ville'; but you'd be looking at a real tentacle of a cable if you wanted to move serious energy.

Most electronic designers are competent enough to put a choke at their power line and a bandpass filter at their cabling. It's not "easy" but it's done in just about any military grade electronics. I guess Boeing engineers didn't think it was necessary.

Some of these planes and designs are well over 30 years old. I doubt they thought back then that people would each have three or four mobile transmitters let alone the idea of putting in a big transmitter inside the cabin to coordinate a bunch of little ones.

Most electronic designers are competent enough to put a choke at their power line and a bandpass filter at their cabling. It's not "easy" but it's done in just about any military grade electronics

And to play a violin all you need to do is to draw the bow across the strings. There's a lot more to this than theory.

A choke is inductive at a limited range of frequencies, at other frequencies it acts as a capacitor. Likewise, put a high enough frequency across a capacitor and its behavior becomes inductive. Electromagnetic compatibility (EMC) is a very complex subject, there are no easy solutions and it's nearly impossible to have a perfect solution that works at all frequencies.

The 2.4 GHz band used in WiFi is one of the most difficult to shield. All the small metallic parts used in electronic equipment, like screws and button levers, are in the same size magnitude as the wave, so there are plenty of conductive parts to retransmit and conduct the radio frequency.

A resonant antenna can be found in PCB traces that are the right length, yes. These traces are usually shielded to the nines, so that stray signal does not get in. Transmission cable is also shielded to prevent extra noise coming in (there's enough of it at the antenna already). Non-shielded cabling (i.e. power) is usually protected from the sensitive stuff by means of an inductor (often called an RF choke) to block off as much of that extra noise as possible. On top of that, Antennas can be designed with a

The only way to make extremely RF tolerant electronics is to use analog vacuum tube based designs (the Russians continued using tube designs into the 90's).

Tube-based designs are no more tolerant than semiconductor-based designs, as far as interference is concerned. What tube-based circuits DO tolerate better is EMP's, (Electro-Magnetic Pulses), from sources such as nuclear blasts - that's why the Russians continued using vacuum tubes. EMP's will damage or destroy destroy most semiconductors within range, (often even in equipment that isn't powered at the time), but properly hardened vacuum tube circuits usually survive.

My guess is that you are not an EE.But you don't have to be to understand it in simple terms. navigation systems work in large part by picking up relatively weak RF signals. It isn't easy to do that when you have a bunch of RF transmitters sitting next to it.Kind of like trying to listen to someone wispier in a rave.

Yeah, but this isn't a navigation system itself, it's a display unit. I agree that nav systems such as VOR/ILS, TACAN, etc. are very interference-susceptible, which is the reason for "all electronic devices off during takeoff/landing" - but that's not actually the case here.

I guess you're not an EE either, then, because no communication system uses pure, unmodulated frequencies. And anyway, if that extremely high-powered signal is lower in frequency than the other one there's every chance it will contain harmonics that are not necessarily orthogonal to the other signal.

"Orthogonal frequencies...do not interfere at all even when one is extremely high-powered"

Frequencies aren't orthogonal (they're scalars), signals are. If you don't control both signals, you can't control orthogonality. One must also consider the dynamic range of the front end - if overloaded with a high powered signal, the frequency relationship doesn't matter. That calls for good bandpass and roofing filter design.

My guess is you're not an EE either. Interference doesn't quite work like that; orthogonal frequencies, for instance, do not interfere at all even when one is extremely high-powered.

And I'm guessing that you aren't an RF engineer.

It is extremely difficult (and nearly impossible, at a reasonable cost) to design and build a transmitter that only radiates RF on the fundamental frequency. It invariably radiates on harmonic frequencies (integer multiples of the fundamental). FCC regulations limit the acceptable power level for harmonics, but if the transmitter's primary power output is high enough, the harmonics can still interfere with a nearby receiver -- depending on the local str

The navigational equipment should be designed so it is tolerant of this sort of interference.

Perhaps it will be going forward. However the average age [bts.gov] of an aircraft you fly in today is probably in the neighborhood of 11 to 12 years old. Which means the designs for these planes are even older. Since WiFi wasn't very common (if it was at the consumer level in some cases)when the current planes were designed, it's a little silly to state the current fleet should be designed to be tolerant of it.

Maybe it will be possible to retrofit active designs in the future, but I'd guess the cost involved will be

My understanding(admittely layman's) is that not all devices are Part 15 devices. Part 15 is basically the "Go ahead and use the shitty parts of the spectrum, or have a less than totally RF-tight case; but don't fuck it up for any of the real people" license.

I'm guessing that aircraft systems may well be held to stricter standards in terms of rejecting interference; but may or may not be required to accept any interference received.

My friend works for a company that makes video distribution systems for airlines (such as Lufthansa). The amount of testing that goes into it is crazy. He's one of the guys who runs all the tests in a Faraday cage and what not. The connectors they have to use to meet FAA regulations and all that are crazy.. the plugs have 16 mini-philips head screws in them to keep the plug from ever working its way loose among other things. They also use Cat 6 and 7 cables for the distribution.. he said no fiber optic lin

oh I've seen it alright... When taking photographs so I could write the removal and installation instructions for the fiber-optic databus on the Eurofighter, I got mad when I saw the assemblers were standing on the fiber-optic harnesses while fitting other items into the avionics bays...

Also, the coaxial cable used to transmit RF signals from the detector heads on the top of the fins on Tornado aircraft have to pass right down the spine tunnel and the slightest over tightening of the cable ties used to secu

Wait... so basically he's saying that they can't use fiber because the techs building and repairing the aircraft are incompetent?

No, basically he's saying that the technicians who build and repair systems are technicians and not fully-trained RF and electrical engineers.

How is "x fastener should only be y tight" any different from "the bolt holding this important piece of engine together should be torqued to y ft-lb?"

Because there are torque wrenches designed to be used to tighten bolts and nuts, that are calibrated by the maintenance crew. While some cable tie guns have adjustments, they are uncalibrated and subject to many factors that make them unreliable -- at least to aircraft standards. I've had cable ties "cut" while still loose just because the tie bound up; I've had the

The West Wing had a quote from Toby Ziegler that essentially sums up how I feel about this:

Toby Ziegler: "We're flying in a Lockheed Eagle series L1011. It came off the line 20 months ago. It carries a Sim-5 Transponder tracking system. Are you telling me I can still flummox this thing with something I bought at Radio Shack?"

That phrase has always bugged me, since the L1011 ended production in 1984 and The West Wing didn't start airing until 15 years later... come on, get the time lines correct! Other than that, brilliant series and very sad to see it go:(

I can make a Tesla coil out of $50 of junk surplus parts and destroy a roomful of the highest end electronic equipment in the world. Hell, a simple spark gap in the right place can cause a world of hurt.

RF energy doesn't give a fuck where you bought something.

You cannot fully shield a device that is specifically designed to receive external signals. In aerospace there's guys who do nothing but electromagnetic compatibility engineering, and not all the threats are external. Sometimes the third side lobe of your strike radar reflects off a rib in the fuselage and the seventh harmonic frequency takes out your very sensitive radar altimeter during initial power up tests.

I do not expect to use any electronics that transmit or receive radio data on a flight. However, as an engineer I do expect that someone will forget to turn off the radio on their device. Thus if I was designing flight control hardware, I would want to ensure that my equipment would not be adversely affected by someone who forgot to turn off their device(s).

The Epic Fail is yours. Specifically your desire to spout off about things you don't know about. Hey, why don't you study RF for a few years then put your opinion in? no, of course not. RF engineering is hard and takes smart people, and you are lazy and stupid.

Given the relatively stringent standards for commercial pilots(who are likely the bulk of 737 fliers, along with a few uber-wealthy VIPs who have a personal motivation to hire good pilots, these aren't your single-engine hobbyist-killers here), "bring one down" is almost certainly a severe overstatement.

flawwed isn't a word in English but there ARE English words that have the "ww" combo, that combination was fairly rare and you often tend to see them separated into word phrases but glowworm, powwow, and arrowwood are real words in English.

But there is one word which is quite common -- if you consider acronyms to be "real" words (and only Scrabble seems to think they aren't) -- then WWW is probably the most common.

And instead of the navigational equipment being built to tolerate wifi interference, we can soon look forward to turning in our terrorist cell phones at the security check, right before "the anonymous machine" checks your prostate. Because we live in a free country!

I actually agree, it was solely meant as a mockery, an extreme exaggeration.

While it indeed is a private entity offering this service, this doesn't mean one can't discuss how this private entity treats its customers. Secondly, the security is put in place by the airport, usually ruled by the countrys laws. The airlines themselves can't make too many demands.

Some years ago I was in a plane ready to take off when the cabin informed of "technical difficulties"

They went searching in a particular area of the seats and found someone who had forgot to turn off his phone before leaving his coat in the luggage compartment(*). It was more educational than a ton of posters asking me to turn off my cell phone.

So... well, let's say that I am that moron that will ask you politely to stop talking when the plane is going to start the take off, even if that means interfering w

I can't imagine a wireless signal interfering with a hardwired display this badly, so is this more an issue with wifi interfering with various sensors that feed the display, causing the system to momentarily "blank" the screen rather than present spurious and inaccurate data?

True shielding can be applied; however, the cost is weight and money. For aircraft, weight is the more important factor. Plus shielding is not always simple. I only know of two planes that have undergone the effort; the twin 747s that serve as Air Force One. I think they had to strip the planes done to the frame and methodically shield everything. I think it took 18 months or something like that.

But shielding adds weight which means increased fuel costs for the operator. This is they typical aviation scenario: until a plane is downed and people die, they'll take the cheap option and pretend that potential problems can't be avoided by proper engineering. It's cheaper to tell people to turn off their devices, cross fingers and pray that everyone complies and nothing happens.

As everyone has said so far, this is a serious fail on the part of Honeywell for not accounting for WiFi in their engineering & testing process. But you can be darned sure this incident will be quoted for the next couple of decades by defenders of "you must keep your devices off when on board" policies. So thanks, Honeywell, for being the instrument of keeping us in the dark ages aboard aircraft.

Let us be sure to publicize this fact every time the subject comes up so that Honeywell's name is eventually equated with the Honey Bucket Man. Not shielding electronics used in airplanes is incompetence at best.

Planes fail from cascade events that always start with something innocuous. OTOH, the fact that you think a wi-fi signal and a 'solar storm' are the same thing, and that you think a 'solar storm' currently doesn't have an impact on nav control point to one fact: You are an ignorant fuck.

So if I open up my laptop and start using it, it starts seeking wifi signals. Is this enough to interfere with the plane?

'cause I don't ever hear flight attendants telling people to disable their wifi (or bluetooth, etc.). Just to "turn off" cell phones. Which itself is weird, 'cause I can leave mine on and put it in airplane mode, right?

'cause I don't ever hear flight attendants telling people to disable their wifi (or bluetooth, etc.). Just to "turn off" cell phones. Which itself is weird, 'cause I can leave mine on and put it in airplane mode, right?

Every time I fly I hear the flight attendants tell us to power down the device completely, they usually specify that airplane mode is not ok. I've always assumed this was because they have no way if knowing of anyone actually put the thing into airplane mode or not.

Of course I don't know that that has anything to do with wireless transmission interference. They might just do it to make sure people aren't distracted by their electronic gadgets and actually listen the safety briefing.

Every time I fly I hear the flight attendants tell us to power down the device completely, they usually specify that airplane mode is not ok. I've always assumed this was because they have no way if knowing of anyone actually put the thing into airplane mode or not.

I fly frequently on various airlines and have never heard "Airplane mode is not OK" or even any reference to "Airplane mode" at all. What airline do you fly?

Flying from Heathrow to Johannesburg on British Airways, the stewardess explicitly said Flight Mode was not acceptable("turn the device off even if the device has a flight mode"), the device had to be off. Flying back from Johannesburg to Amsterdam on KLM, the stewardess explicitly said Flight Mode was acceptable ("turn the device off or put it into flight mode"). The outbound flight was on a 747-400 and the flight back was on a 777-200.

Yup. This is because ILS is an old and very finicky interference-sensitive system (It basically relies on determining where within an RF "pencil beam" coming from the end of the runway you are). The concern is that leakage from just the clocks in an active device could throw off the ILS system's accuracy.

Once you're airborne, ILS doesn't matter, and the remaining navigational systems are far less interference-prone.

More likely it has to do with other passengers believing a rogue cellphone might crash the plane and may complain to the flight attendant if they see another passenger using a cellphone. The other passenger has no idea if airplane mode is in use.

Rather than risking a headache of explanation or calming down snippy passengers, it's easier for the attendant to just tell everyone to turn them all off. They don't really stand to gain anything by splitting hairs over with someone over what's ok and what's not ok.

Actually, last time I was on a plane (Airtran), they said all wifi-capable devices must also be turned off. Too bad they don't actually turn off their wifi router; they just redirect you to a page saying all wireless devices should be turned off. I guess wireless routers that broadcast within these frequencies are ok because as long as they aren't actually accomplishing anything then the radio waves coming from it magically become less dangerous or something.

The ban on electronic devices in general is for no other reason than to force you to pay attention. Takeoffs and landings are the most critical phases of flight where the most can go wrong. They want your maximum attention during these times in case of an emergency. Yelling brace brace isn't gonna get through if everybody's got their MP3 players turned up to 11. That's why they still let you have your headphones plugged in to the in seat entertainment system, because any announcements pre-empt whatever you'

Not only is it for one specific module, its only at elevated power levels, not typical power levels. Lets watch the corporate media fuck this up and turn into a scare tactic to show more ads to morons.

Boeing, meanwhile, says: "Current testing by Boeing and Honeywell has determined that blanking may occur when a DU is subjected to testing procedures specified by the FAA requirements (AC-20-164) during installations of Wi-Fi systems on the airplane. Based on testing that has been conducted, Boeing and Honeywell have concluded that actual EMI levels experienced during normal operation of typical passenger Wi-Fi systems would not cause any blanking of the Phase 3 DU. This issue does not exist with the Phase 1 or 2 DU's."Honeywell says that, during recent ground testing "at elevated power levels", the company observed a momentary blanking on the 'flat panel' liquid crystal displays that it developed and pioneered for Boeing."The screens reappeared well within Boeing's specified recovery time frame. The screens have not blanked in flight and are not a safety of flight issue. Honeywell is working to ensure the problem is addressed and fixed and that our technology will continue to exceed specifications," says Honeywell.

This is just another example of how (inexplicably to me at least) companies want to continue fear based rules that just don't make sense. It's like the whole "don't use your cell phone near the gas pump" BS that they tried to spread for a long time. Even when tests and common sense says there's no way a cell phone would cause a spark that would ignite gas fumes unless some catastrophic (and extremely rare) occurred.

So the company just admitted that their (likely expensive) aviation equipment (displays?) are more error prone from EMI than say....my desktop pc...phone...digital watch? What sort of equipment are these people working with? Consumer electronics are bombarded by this sort of EMI constantly and I don't see any displays blanking in my office. In an airplane I would have assumed they would have to have MORE shielding because at altitude they have less shield from solar radiation which is well known for being harmful to electronics where my wifi adapter hasn't fried a single piece of electronics...yet.
This still sounds like total BS to me.

Actually if you look through details, it sounds like an EMI hole below that which is specified by the relevant standard was within the 2.4 GHz band.

This hole was nowhere near deep enough for a WiFi device to actually exceed the threshold, but the FAA is VERY conservative when it comes to civilian airliners - Any hole in that band = eliminate all transmitters in that band just to be sure.

In other news, university officials have noticed a sharp increase in the number of terrorists applying for admission to EE degree programs. Until now, terrorists have traditionally favored chemistry and chemical engineering programs. Chem E applications have dropped sharply.

Chem E prof: "I really don't understand it. We still have a great program, Although it was strange: all that these students seemed interested in, were exothermic reactions.

...and I say thank all that's holy for that. Anything that keeps airplanes as the one place that I'm not going to be bothered by "CAN YOU HEAR ME NOW?" or disturbingly personal/intimate conversations of total strangers is entirely welcome to me. Give me one refuge from connectivity, please, just one.

I've never understood why people call this a myth. Whenever I'm sitting near speakers and my cell phone decides to check in with the tower, I hear a distinct beeping noise. If I can *hear* the effect of a signal, why do people think that a switch can't flip because of it? I don't want to die in a fireball of doom because you wanted to tweet that the guy next to you on the plane just farted.

So the title is wrong. It should read. "It is possible to build an airplane that can pick up WiFi signals". This isn't a case of Wifi being able to interfere with "Airplanes" as in the generic term "Airplanes". This is a case of one system that has never been shipped being faulty, and picking up Wifi signals. This is Wifi "being able to interfere with planes" as much as "loud chanting can interfere with planes". No doubt Honeywell could build one of those too. Heck, I'm sure if they put their mind to

Let me ask yourself: when you are in a plane... are there, now, other WiFis to which you can connect? Not someone else's computer that is useless (unless you want to have a LAN party), but something that will give you internet access?

Even if Boeing is designing that "new" Wi-Fi that you guess, they do not need to deliver FUD to become the only operator. In fact, this only discourages Wi-Fi usage (yes they can claim later its Wi-Fi is safer, but some doubt will remain...)